Massive MIMO (multiple-input, multiple output) systems typically include a large number of antennas. Accordingly, the performance of such systems is very sensitive to the accuracy of channel knowledge. Further, some massive MIMO systems, such as implementation using drones or wind sensitive high tower deployments suffer from random movements of either the antennas.
It is desirable to have methods apparatuses, and systems for precoding MIMO (multiple-input, multi-output) signals according to identified zones of users.
Summary
An embodiment includes a method of zone precoding. The method includes determining a precoding of transmission signals to each of a plurality of users from a base station, and applying the precoding of each user to wireless communication signals communicated between the base station and the user. For an embodiment, the transmission zone includes an angle of direction of a directional beam from the base station to each user, and a deviation of the angle of direction of the directional beam. For at least some embodiments, determining a precoding of transmission signals to each of the plurality of users from the base station, includes determining an initial precoding for each of the users based on the transmission zone associated with the user, wherein the initial precoding is selected to provide a received power at the user that deviates by less than a threshold over the transmission zone, and constructing the precoding for each user comprising adjusting the initial precoding for each user based on the transmission zone determined for each of the other users.
Another embodiment includes a base station. The base station includes a plurality of antennas, a plurality of radios connected to the plurality of antennas, and a controller. The controller operates to determine a transmission zone for each of the plurality of users, wherein the transmission zone includes an angle of direction of a directional beam to each user from the base station formed by the plurality of antennas, and a deviation of the angle of direction of the directional beam. The controller further operates to determine a precoding of transmission signals to each of the plurality of users from the base station, including determine an initial precoding for each of the users based on the zone associated with the user, wherein the initial precoding is selected to provide a received power over the transmission zone of the user that deviates by less than a threshold, and construct the precoding for each user comprising adjusting the initial precoding for each user based on the transmission zone determined for each of the other users. The controller further operates to apply the precoding of each user to wireless communication signals communicated between the plurality of antennas of the base station and the user.
Embodiments according to the invention are in particular disclosed in the attached claims directed to a method and a base station, wherein any feature mentioned in one claim category, e.g. method, can be claimed in another claim category, e.g. base station, system, storage medium, and computer program product, as well. The dependencies or references back in the attached claims are chosen for formal reasons only. However any subject matter resulting from a deliberate reference back to any previous claims (in particular multiple dependencies) can be claimed as well, so that any combination of claims and the features thereof is disclosed and can be claimed regardless of the dependencies chosen in the attached claims. The subject-matter which can be claimed comprises not only the combinations of features as set out in the attached claims but also any other combination of features in the claims, wherein each feature mentioned in the claims can be combined with any other feature or combination of other features in the claims. Furthermore, any of the embodiments and features described or depicted herein can be claimed in a separate claim and/or in any combination with any embodiment or feature described or depicted herein or with any of the features of the attached claims.
In an embodiment according to the invention, a method may comprise training a transmission channel between a base station and each of a plurality of users, wherein the base station comprises a plurality of antennas that operate to form directional beams to each of the plurality of users, comprising determining a transmission zone for each of the plurality of users, wherein the transmission zone includes an angle of direction of a directional beam to each user, and a deviation of the angle of direction, determining a precoding of transmission signals to each of the plurality of users from the base station, comprising determining an initial precoding for each of the users based on the transmission zone associated with the user, wherein the initial precoding is selected to provide a received power at the user that deviates by less than a threshold over the transmission zone, constructing the precoding for each user comprising adjusting the initial precoding for each user based on the transmission zone determined for each of the other users, and applying the precoding of each user to wireless communication signals communicated between the base station and the user.
Determining the transmission zone for each of the plurality of users may comprise determining a direction to the user, determining an indicator of a stability of the plurality of antennas of the base station.
Determining the transmission zone for each of the plurality of users may comprises determining a direction to the user, determining a distance between the user and the based station, and determining a level of mobility of the user.
Determining the transmission zone for each of the plurality of users may comprises determining a cone covariance matrix of radius r for each of the users, wherein r is based on the deviation of the angle of direction.
Determining the cone covariance matrix may comprise determining every element of the cone covariance matrix over the transmission zone, wherein the transmission zone is defined by the direction and radius r.
Determining each element of the cone covariance matrix may comprise determining a covariance between pairs of antenna elements n and m over the transmission zone.
Determining the initial precoding of each user for communication between the base station and each of the users may comprise constructing an initial precoding vector for each user.
Determining the initial precoding vector for each user may comprise:
determining a dictionary matrix A that includes a set of vectors, wherein each vector of the set of vectors defines a quantized direction in an angular domain; and
constructing initial precoding, using a least square method, for each user to ensure a target received power over a set of vectors of the dictionary matrix A that define the transmission zone of the user.
Adjusting the initial precoding for each user based on the transmission zone determined for each of the other users may comprise determining an interference nulling matrix for the user for the transmission zones of other users.
Determining the interference nulling matrix may include determining subspaces of the interference nulling matrix to ensure that a signal transmitted by the user does not cause interference in transmission zones of the other users.
Determining the precoding may comprise determining a precoding matrix, wherein the precoding matrix may include a precoding vector for each user.
Determining the precoding matrix may comprise constructing the precoding vector for each user by projecting an initial precoding vector of the user on interference nulling matrices of the other users.
In an embodiment according to the invention, a base station may comprise a plurality of antennas, a plurality of radios connected to the plurality of antennas, a controller, wherein the controller operates to determine a training of a transmission channel between the plurality of antennas of the base station and each of a plurality of users, wherein the plurality of antennas operate to form directional beams to each of the plurality of users, comprising determining a transmission zone for each of the plurality of users, wherein the transmission zone includes an angle of direction of a directional beam to each user, and a deviation of the angle of direction, determine a precoding of transmission signals to each of the plurality of users from the base station, comprising determine an initial precoding for each of the users based on the zone associated with the user, wherein the initial precoding is selected to provide a received power over the transmission zone of the user that deviates by less than a threshold, and construct the precoding for each user comprising adjusting the initial precoding for each user based on the transmission zone determined for each of the other users, and apply the precoding of each user to wireless communication signals communicated between the plurality of antennas of the base station and the user.
Determining the transmission zone for each of the plurality of users may comprise determining a cone covariance matrix of radius r for each of the users, wherein r is based on the deviation of the angle of direction, and wherein determining the cone covariance matrix comprises determining each element of the cone covariance matrix over the transmission zone, wherein the transmission zone is defined by the direction and radius r, wherein determining each element of the cone covariance matrix comprises determining a covariance between pairs of antenna elements n and m over the transmission zone.
Determining the initial precoding of each user for communication between the base station and each of the users may comprise constructing an initial precoding vector for each user, which may comprise determining a dictionary matrix A that includes a set of vectors, wherein each vector of the set of vectors defines a quantized direction in an angular domain; and constructing initial precoding, using a least square method, for each user to ensure a target received power over a set of vectors of the dictionary matrix A that define the transmission zone of the user.
Adjusting the initial precoding for each user based on the transmission zone determined for each of the other users may comprise determining an interference nulling matrix for the user for the transmission zones of other users.
Determining the interference nulling matrix may include determining subspaces of the interference nulling matrix to ensure that a signal transmitted by the user does not cause interference in transmission zones of the other users.
Determining the precoding may comprise determining a precoding matrix, wherein the precoding matrix may include a precoding vector for each user.
Determining the precoding matrix may comprise constructing the precoding vector for each user by projecting an initial precoding vector of the user on interference nulling matrices of the other users.
In an embodiment according to the invention, a method may comprise: training a transmission channel between a base station and each of a plurality of users, wherein the base station comprises a plurality of antennas that operate to form directional beams to each of the plurality of users, comprising determining a transmission zone for each of the plurality of users, wherein the transmission zone includes an angle of direction of a directional beam to each user, and a deviation of the angle of direction, selecting a precoding of transmission signals to each of the plurality of users from the base station to provide a received power that deviates by less than a threshold over the transmission zone, and wherein received interference within transmission zones of other users is below a threshold, and applying the precoding of each user to wireless communication signals between the base station and the user.
In an embodiment according to the invention, one or more computer-readable non-transitory storage media may embody software that is operable when executed to perform a method according to the invention or any of the above mentioned embodiments.
In an embodiment according to the invention, a system may comprise: one or more processors; and at least one memory coupled to the processors and comprising instructions executable by the processors, the processors operable when executing the instructions to perform a method according to the invention or any of the above mentioned embodiments.
In an embodiment according to the invention, a computer program product, preferably comprising a computer-readable non-transitory storage media, may be operable when executed on a data processing system to perform a method according to the invention or any of the above mentioned embodiments.
Other aspects and advantages of the described embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the described embodiments.